gcse biology

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  • Created on: 27-10-12 11:44

diet and exercise

Healthy diet

you need enough....

  • carbohydrates to release energy,
  • fats to keep warm and release energy
  • protein for growth, cell repair and cell replacement
  • fibre to keep everything moving smoothly through your digestive system,
  • tiny amounts of various and mineral ions to keep your skin, bones, blood and every thing else generally healthy. 

Unbalanced diet

People whose diet is badly out of balance are said to be malnourished.

malnourished people can be fat or thin, or unhealthy in many ways.

exercise is important just as healthy diets. usually people who exercise are usually healthier.

exercise increases the amount of energy and gets rid of loads of fat.

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diet and exercise continued.

Energy chart

Activity                   KJ/min

sleeping                    4.5

watching tv                 7  

cycling (5mph)            21

jogging (5mph)            40

climbing stairs            77

swimming                   35

rowing                        58

slow walking               14

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There are 2 main types of pathogen; bacteria and viruses.

  • bacteria are very small living cells. they also reproduce very quickly. 
  • they make you feel ill by doing 2 things : damaging your cells and producing toxins.
  • viruses are not cell - they are much smaller.they produce copies of themselves by splitting in half. this cell will usually burst releasing new viruses. this cell damage makes are feel ill.


They protect from future diseases. they involve injecting amounts of inactive microorganisms. some vaccines 'wear off' over time.


  • have helped control lots of diseases e.g. polio, measles, smallpox .....
  • big outbreaks of disease can be prevented.

but don't always work ,sometimes have a bad reaction 2 the vaccine.

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nervous system and control in humans

Nervous system

sense organs detect stimuli

the 5 sense organs

1) eyes - light receptors - sensitive to light.these cells have a nucleus, cytoplasm, and cell membrane

2) ears - sound receptors - sensitive to sound. also balance receptors - sensitive to changes in possision

3) nose - smell receptors - sensitive to chemical stimuli

4) tongue - taste receptors - sensitive to bitter, sweet, salt and sour, plus the taste of savoury things like msg -chemical stimuli

5) skin - sensitive to touch , pressure, pain and temperature change.

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drugs and drug trialling

Drugs change your body chemistry. some drugs can be used as medicine but some are also illegal which are recreational drugs or performance-enhancing.

Some athletes take performance enhancing drugs to make them better at sport. there are two different types of them in many ways including steroids which increase muscle size and stimulants which increase heart rate.

medicine drugs are legal and you don't always need a prescription for them. but for others you do.

recreational drugs are used for fun but are illegal. stuff like include cocaine and marahuana.

Drug trialling 

first the drug is tested on healthy volunteers to make sure it doesn't have any harmful side affects. at the start a very low dose is given and then increases.

if there are 4 people 2 people will have the real drug and 2 people will have the fake one. only the people giving the doctors who are giving the volunteers know which volunteers have the real drug.

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Adaptations and environmental change

desert animals have adapted to save water and keep cool.

Large surface area, efficient with water, good in hot conditions and are camouflaged.

Arctic animals have adapted to reduce heat loss.

small surface area, well insulated and camouflaged.

desert plants have adapted to having little water.

small surface area compared to volume, water storage tissues and maximising water absorption

some plant and animals are adapted to deter predators.

some plants and animals have armour.

others produce poisons

some have warning colours to scare of predators.

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Energy in biomass

100 dandelions feed 10 rabbits which feeds 1 fox.

                   pyramid of biomass

                          . fleas




the big bar along the bottom represents the producer e.g. plants

the next big bar will be the primary consumer. 

then the secondary consumer

and so on up the food chain......

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variation and reproduction

different genes causes different variation. organisms of the same spices have differences. characteristics are also influenced by the environment. most characteristics are due to genes and the environment.

sexual reproduction produces genetically different cells. sexual reproduction involves the fusion of male and female gametes. because there are two parents, the offspring contain a mixture of their parents' genes.

asexual reproduction produces genetically identical cells. in asexual reproduction there's only one parent. there's no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. the offspring are genetically identical (clone) to the parent

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Evolution and natural selection

All organisms are related... even if only distantly.

Evolution can occur due to mutations.

Natural selection explains how evolution occurs.

individuals in a species show variation because of the difference in genes.

individuals with characteristics that make them better adapted to the environment are more likely to survive and are more likely to breed successfully.

so, the genes that are responsible for the useful characteristics are more likely to be passed on to the next generation.

By Joshua Andrews

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the carbon cycle

pic of the carbon cycle


the whole thing is powered by photosynthesis.

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